Given the equations below what is the value of ab?

10b-9a=6

b-a=1

12

Step-by-step explanation:

Adding a to both sides of the second equation we get b = a+1

Substituting this in we get

10a + 10 - 9a=6

a + 10 = 6

a=-4

Putting this back in to the second one we get b+4=1

B=-3

-4*-3=12